Mac mini 2011 & Dolby Atmos & PHT & the future...

Hi all

Been using Plex for 5+ years but recently got Atmos equipped. I've googled and really need a tl;dr...

I assume because of the limitations of OS X, I cannot get Atmos content to play on my receiver with the receiver screen saying specifically "Dolby Atmos". Currently I have sound coming out of all speakers, but it says PCM (but Dolby Digital etc shows up fine)...

1. I assume PCM is not passthrough.
2. I also assume I'm not hearing everything how Dolby wishes?
3. Should all the encoding boxes (DTS) etc be ticked on an OS X machine?
4. I guess we wait for late-2016 Mac mini to fix everything!?